Re: [RFC][PATCH 12/12] PM / r8169: Add simplified run-time PM support

Pavel Machek
2010-01-04T08:31:08Z

> > > Using /proc/acpi/battery/BAT1/state I measured the energy drawn in 10 minutes
> > > both with the network adapter in D0 and D3hot. The results were that with the
> > > network adapter in D0 the box drew 2476 mWh, while with the network adapter in
> > > D3hot it drew 2361 mWh. The difference is 115 mWh, or about 5% on this
> > > particular box.
> > >
> > > This means about 0.1 Wh in 10 minutes, so we can save about 0.6 Wh per hour.
> >
> > Which means it saves 0.6W :-). Measuring power in Wh/h is "interesting".
>
> You can't save power, you can only save energy. Wh is just an energy unit.

Of course we can save power, you just did :-).

(And in some cases -- data centers, limited cooling -- you are limited
by power, not energy. You are right that on notebooks, energy is more
important.)

Pavel

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